The present invention is directed to a process to prepare a sweet crude from an ash containing and heavy fraction of a tar sand oil.
Such a process is described in U.S. Pat. No. 6,702,936.
In this process various distillate fractions of a tar sands feed are subjected to a hydroprocessing step to obtain a sweet synthetic crude. From a vacuum residue fraction of the tar sands feed an asphalt fraction is isolated and fed to a gasification unit to obtain a mixture of carbon monoxide and hydrogen. From this mixture substantially pure hydrogen is recovered and used in the hydroprocessing unit.
A disadvantage of this process is that it is sensitive for process failure. For example the hydroprocessing unit requires a very high availability of hydrogen. On the other hand it is known that gasification units and de-asphalting units do not have the high reliability to ensure a high hydrogen availability.
The present invention provides a solution to the above problem.